Question [Q] Nexus 5 D820 works only on 2G

Hi,
I bought a new device, Nexus 5 D820.
And I have a problem when I insert SIM regardless of which provider I have no reception (no service),
Tried to set the correct APN settings with the provider but it didn't help.
It works out only when I'm working on 2G when I return to 3G again no reception. (No LTE in my country)
what could be the problem?